Method for selective herbicidal treatment of cereal and carrot cultures

ABSTRACT

N-(3-chloro-4-methoxyphenyl)-N&#39;&#39;,N&#39;&#39;-dimethylurea of the formula:   IS DISCLOSED AS POSSESSING A SURPRISING SELECTIVE HERBICIDAL ACTIVITY. A method is disclosed for selectively combating weeds in a cereal locus and a carrot locus, which comprises applying to the locus to be protected from weeds, a dosage of from 2 to 10 kilograms per hectare of the above compound.

United States Patent Schuler [111 3,865,571 [45'] Feb. 11, 1975 [75]Inventor: Max Schuler, Arlesheim,

Switzerland {73] Assignee: Sandoz Ltd.. Basle, Switzerland [21] Appl.No.: 275,506

Related U.S. Application Data [63] Continuation-impart of Ser. No.882,293, Dec. 4, 1969, abandoned, which is a continuation-in-part ofSer. No. 743,589, July 10, 1968, abandoned, which is a continuation ofSer. Nos. 583,108, Sept. 29, 1966, abandoned, and Ser. No. 583,109,Sept. 29, 1966, abandoned.

[52] U.S. Cl. 71/120 [51] Int. Cl A0lh 9/20 [58] Field of Search 71/120[56] References Cited UNITED STATES PATENTS 2,655,445 10/1953 Todd71/120 2,655,447 10/1953 Todd 71/120 3,288,851 11/1966 Martin et a1.71/120 OTHER PUBLICATIONS Thompson, Agricultural Chemicals-Book11-Herbicides (1964).

Harris, Chem. Abst., Vol. 58, 9571e.

Primary Examiner-Lewis Gotts Assistant Examiner-Catherine L. MillsAttorney, Agent, or Firm-Gerald D. Sharkin; Richard E. Vila [57]ABSTRACT N-(3-chloro-4-methoxypheny1)-N,N dimethylurea of the formula:

is disclosed as possessing a surprising selective herbicidal activity. Amethod is disclosed for selectively combating weeds in a cereal locusand a carrot locus, which comprises applying to the locus to beprotected from weeds, a dosage of from 2 to 10 kilograms per hectare ofthe above compound.

11 Claims, N0 Drawings METHOD FOR SELECTIVE HERBICIDAL TREATMENT OFCEREAL AND CARROT CULTURES This application is a continuation-in-part ofour copending application Ser. No. 882,293, filed Dec. 4, 1969, nowabandoned which is in turn a continution-inpart of our application Ser.No. 743,589, filed July 10, 1968 and now abandoned, which in turn is acontinuation by consolidation of our applications Ser. Nos. 583,108 and583,109, both filed Sept. 29, 1966 and both now abandoned.

The present invention relates to a method of selectively combating weedsin a cultivated plant locus and more specifically to a method ofselectively combating weeds in a cereal, e.g. wheat, locus or a carrotlocus.

The use of aryl urea derivatives for combating weeds has been known forsometime. As long ago as 1946, H. E. Thompson et al. reported plantgrowth inhibition by aryl urea derivatives [Botan. Gaz. l07 476-507(l946)].

Some time later, the compound monuron (trade name forN-(4-chlorophenyl)-N ,N'-dimethylurea) was introduced as a totalherbicidal. Following the commercial introduction of monuron, asuccession of related compounds were also made available as totalherbicides. Of such related compounds fenuron (trade name forN-phenyl-N,N'-dimethylurea) and diuron (trade name forN-(3,4-dichlorophenyl-N',N'- dimethylurea) may be mentioned as the mostimportant.

These compounds are characterised by an N',N- dimethyl residue. Furtheraryl urea derivatives were later developed having instead of anN,N'-dimethyl residue of the earlier total herbicides, an N-methoxy-N-methylamino residue.

Attention however was still concentrated on the earlier totalherbicides, and eventually it was discovered that such herbicides at lowdosages, under the right conditions and in certain crops did in factoperate to selectively combat weeds in pre-emergence treatment of thecrop locus. It was, and still is, of course recognised, however, thatsuch selectivity is accompanied by the risk of considerable crop damage,e.g. in the case of heavy rainfall, unsuitability of the soil and overdosing, since the earlier aryl urea are basically total herbicides.Moreover, as is well known, a crop plot, having been surface treatedwith the total herbicides, cannot be replanted within at least 1 yearand sometimes 2 years, without serious risk of loss of the subsequentcrop owing to the high residual effect of the aryl urea. Indeed, atpresent, their main practical use is in soil sterilisation.

The selective mode of action of the earlier aryl ureas in thepre-emergence treatment of crops has been explained on the basis oftheir low water solubility and their tendency to remain in the surfacelayers of the soil. Since they are highly effective at killing youngseedling plants following uptake thereof through the roots from thesoil, weeds, which are frequently shallow germinating and have at leastsome roots near the soil surface will be eradicated by the herbicidetreated surface layers. The root zones of crop plants on the other hand,which are the herbicide sensitive region of the plant, hardly contactthe herbicide treated surface layer since they are generally disposeddeeper in the soil below said layer. it will be appreciated thereforethat by such mechanical selectivity, the crop plant may survive, itsstem being relatively herbicide insensitive and passing through theherbicide treated surface layer, while the weeds are eradicated. It willalso be appreciated however, that such mechanical" selectivity may behighly precarious especially in locations susceptible to heavy rainfallwhereby the herbicide may be leached down through the soil to theherbicide sensitive roots of the crop plant or be washed away intolocalised pools where their total herbicidal activity may be effectivelyexercised. Moreover, such mechanical" selectivity is subject to furtherserious limitations in the case, for example, of the herbicide sensitivezones of the crop plants and weed species being disposed at similardepths in the soil. This is in fact typical of weed grass infestedcereal crops, particularly wheat crops where both the weeds and the cropare members of the grass family.

It is to be understood that some herbicides are now known having aselective mode of action which can only be explained on the basis ofphysiological tolerance of the crop plant to the herbicide. A well knownexample of such selectivity, which relies on a biological as opposed toa mechanical selective mode of action, is the case of the herbicidesimazine (trade name for 2-chloro-4,6-bis-ethylamino-l ,3,5-triazine) inmaize. Such herbicides are however relatively uncommon.

It has now surprisingly been found that a certain aryl urea having anN,N-dimethyl residue exercises an excellent degree of biological"selectivity in cereals and carrots, and moreover has a relativelyshorter residual effect than the earlier total herbicides. This compoundis one of a series of aryl ureas that have been disclosed in US. Pat.No. 2,655,445.

Accordingly, the present invention provides a method of selectivelycombating weeds in a cereal or carrot locus to be protected from weedswhich comprises treatment of the locus with N-(3-chloro-4- in an amountof from 2 to 10 killograms per hectare of locus.

It is to be understood that by cereal locus is meant a locus to be orhaving been sown with cereal seed and the method of the inventionembraces both pre and post-emergence treatment of the cereal crop.Similarly, by carrot locus is meant a locus to be or having been sownwith carrot seed and the method of the invention embraces both pre andpost-emergence treatment of the carrot crop.

The method is particularly applicable to treatment of the locus afterthe cereal or carrot seed, as the case may be, has been sown.

Examples of cereals contemplated within the scope of the method of theinvention are winter and summer wheat, winter and summer rye, and winterand summer barley.

As is well known, an effective and safe method of combating weeds,particularly weed grasses, in wheat is particularly sought after in theart and thus the treatment of a wheat locus is a preferred embodiment ofthe invention. Examples of weed grasses widespread in wheat and againstwhich the method of thepresent invention is effective are Bromustectorum (cheat grass) and Lolium multiform (animal rye grass). It isparticularly notable'that even today, no effective selective control ofBromus tectorum in wheat is available.

The compound can be applied by conventional techniques to the particularlocus at a dose of up to about kilogram per hectare withoutsignificantly affecting the cereal or carrot crop growth. The extent ofthe dose at which the compound may be applied to allow selective growthof the cereal and carrot crops is such that weed growth can be verysuccessfully controlled, even at a dose as low as about 2 kilogram perhectare.

In general, a preferred dose is between 3 to 6 kilogram per hectare,although in the case of carrots, in some cases, a higher dose may bedesirable. As will be readily appreciated by those in the art, theparticular dose selected will vary with such factors as the type ofsoil, climatic conditions and the degree and type of infestation.

The compound has an exceptional and practical effect spectrum. Forexample, it has been found that the compound is effective against suchimportant species as Agrostis alba, Alopecurus spp., Apera spica-venti,Avena fatua, Lolium perenne and Plantago major. The activity of thecompound against Plantago major is indeed unexpected in that theliterature on the subject indicates that N-aryl-N',N-dimethylureas arepractically ineffective against this weed (see, for example E.KJWoodford and S. A. Evans, Weed Control Handbook, 3rd Ed. 1963, page194; and Ph. Jussiaux and R Pequinot, Mauvaises Herbes, Paris 1962, page1 l7).

The compound may be applied before or after germi-. nation of weeds, orbefore sowing of the cereal or carrot seeds, or simultaneously with thesowing of the cereal or carrot seeds, or after the cereal or carrotseeds have been sown, or after germination of the cereal or carrotseeds.

,The compounds of the formula I may be produced in known manner, forexample, by starting with 3-chloro- 4-methoxyphenyl-isocyanate anddimethylamine, or starting with N,N-dimethylcarbamoylchloride and3-chloro-4-methoxyaniline.

The following examples A and B illustrate production of the compound offormula I:

EXAMPLE A 73.4 g (0.4 mol) of 3-chloro-4-methoxyphenyl isocyanate(boiling point 79-89C/0.2 mm of Hg) are added dropwise at 5lOC over 1 to1-hour to 45 g of 40 percent-by weight aqueous dimethylamine solution(corresponding to 0.4 mol of dimethylamine); an exothermic reactiontakes place and, as the reaction proceeds, the product is continuouslyprecipitated in crystalline form. The crystalline precipitate isfiltered with suction, washed with a little water and dried at 50-70C ina water pump vacuum. The compound of formula I is obtained in the formof colourless crystals having a melting point l23l 25C with a yield of82.5 to 87 g (90 to 95 percent of theory). After recrystallization fromethanol, colourless crystals of melting point 126-l27C are obtained.

The compound of formula I is likewise obtained when gaseousdimethylamine is introduced to saturation point into a solution of 0.'lmol of 3-chloro-4- methoxyphenylisocyanate in 200 ml of anhydrous etherat C while stirring well and cooling, the resulting reaction productbeing filtered off with suction and dried.

EXAMPLE B 63 g of 3-chloro-4-methoxyaniline (0.4 mol) and 42 g oftriethylamine are dissolved in 300 ml of dimethylformamide. 45 g (0.418mol) of N,N-dimethylcarbamoylchloride are stirred dropwise into theresulting solution over 20-30 minutes, care being taken by cooling thatthe temperature, which initially should be 20-25C does not rise above30-35C. Shortly after the reaction has commenced, the resultingtriethylamfrom the reaction solution by suction. Dimethylformamide isdistilled off at 0.02 to 0.2 mm of Hg at a bath temperature of 35-45C.The crystalline residue is stirred with 250-400 ml of water whereuponthe required product crystallizes out. Filtering with suction iseffected, washing with a little water is carried out and drying iseffected at 5080C in a water pump vacuum.

The compound of formula I is obtained in the form of colourlesscrystals, which, depending on the purity of the amino compound used, maybe slightly beige to brownish, of melting point l2l-l24C with a yield of78-85 g (83-93 percent of theory). By recrystallizing from-ethanol thereare obtained colourlesscrystals of melting point l25-l27C.

The compound of formulal may be applied to the particular locus byconventional techniques. Thus, the compound may be provided as aconcentrate for dilution with conventional herbicidal diluents. Suitablepreparation forms include solutions, emulsions, suspensions, dustingpowders, strewing agents and granulates. A suitable diluted aqueoussuspension or emulsion ready for use contains 0.005-l percent by weightof the compound I, and the suspension or emulsion may, if desired,contain known agents for facilitating distribution and increasing theadhesive power and resistance to ram.

Application of preparations containing the compound of formula I may beeffected by firstly emulsifying or suspending the preparation in waterand then sprinkling plants to be treated. Application may be effectedbefore or after germination of weeds or crop.

Application may furthermore be effected by dusting weeds to bedestroyed, or by the direct application of the preparation containingthe compound of formula I, said preparation then conveniently being inthe form of a dusting or strewing agent or granulate. If necessary, thepreparation may be worked into the soil.

In the following Examples I to IX some possibilties of producingsuitable preparations containing the compound of formula I and theirconstituents are described.

EXAMPLE I:

Parts by weight of the compound of formula I together with 29 parts byweight of an inert solid carrier, consisting of a mixture of 2 parts ofkaolin, 1 part of diatomaceous earth and 1 part of talcum, and also 1part by weight of an adhesive commonly used for this purpose are, groundto a fine powder in a ball mill; the resulting powder'may be used as adusting agent.

EXAMPLE II:

20 Parts by weight of the compound of formula I together with 72 partsby weight of an inert solid carrier mixture (consisting of /3 ofdiatomaceous earth and Va of kaolin), 6 parts by weight ofisooctylphenyloctaglycol ether and 2 parts by weight of a protectivecolloid, for example, sulphite waste liquor, are ground together to forma fine powder in a stud mill. This powder is suitable for suspension inwater.

EXAMPLE III:

A pulverulent material capable of easy suspension in water is obtainedby mixing and grinding 25 parts by weight of the compound of the formulaI and 3 parts by weight of tertiary dodecylmercaptoundecaglycol ether, 7parts by weight of pulverulent silica gel and 65 parts by weight ofkaolin.

EXAMPLE IV:

20 Parts by weight of the compound of formula I together with 9 parts byweight of isooctylphenylheptaglycol ether, 41 parts by weight of mesityloxide and 30 parts by weight of cyclohexanone are stirred together toform a clear solution which may be used as a liquid spraying agentconcentrate.

EXAMPLE V:

50 g of the compound of formula I, g of pulverulent soy bean albuminextract (spray soy), 5 g of commercially available dextrin, 18 g of asulphonated condensation product of naphthalene and formaldehyde, 4 g ofthe sodium salt of alkylbenzenesulphonate, 2 g of ammonium caseinate and6 g of colloidal silicic acid (Santocel) are ground together in a ballmill to form a wettable powder.

EXAMPLE VI:

EXAMPLE VII:

The suspension obtained according to Example Vl, without addition ofthickener, is carefully evaporated to dryness in a vacuum andsubsequently ground in a ball mill; in this way a wettable powder isobtained which shows excellent suspension properties when it is stirredinto water to give a preparation ready for use.

EXAMPLE VIII A solution in acetone of 20 g of the compound of formula Iis sprayed on 180 g of pumice granulate having a grain size of 0.3 to lmm and the solvent is then removed in the vacuum of a water pump at4060C. A well flowing grainy granulate is obtained.

EXAMPLE IX 5 Parts by weight of the compound of formula I and parts byweight of bentonite are put into a mixer and 10 parts by weight ofdiethyleneglycol are sprayed in while mixing continuously. The resultingmixture is kneaded in a kneader and then granulated to a grain size of0.5 to 1 mm.

The following Examples 1 and 2 describe and set out particulars ofgreenhouse tests carried out with the compound I and also Diuron forcomparison purposes.

EXAMPLE 1:

Pre-emergent treatment Seed dishes measuring 30 X 40 cm are filled to adepth of 6 cm with a mixture of peat culture substrate No. l (Obtainablefrom Torfstreuverband GmbH., 29 Oldenberg, Germany) and sand. Theexposed surface of the peat culture and sand mixture is sprayed with 50ml of a certain percentage by weight solution of herbicide, and 6species of seed are then sown in each dish. The number of seeds sown foreach plant species depends on the seed germination potential and alsothe initial growth size of the particular seed plant. After sowing ofthe seeds, the treated surface is covered with a thin layer about 0.5 cmdeep of the peat culture and sand mixture.

The prepared seed dishes are kept for 28 days at a temperature of 20 to24C and 14 to 17 hours normal summer daylight each day.

Determination of the herbicidal effect of the particular herbicide ismade after the 28 days period. The determination involves a visualevaluation of the degree and quality of damage to the various seedplants. A rating number between 1 and 9, dependent on the extent ofdamage to the seed plant is allocated to each plant species.

As will be appreciated by those in the art, this Example gives anindication of the degree of biological as opposed to mechanical,selectivity since the seeds are sown into a herbicidally treated layerof peat culture and sand mixture and then covered with a further layerof the same.

The results obtained with compound I and Diuron are set out in thefollowing Tables 1 and 2. The weeds employed in the tests are PlantagoMajor Amaranthus retroflexus Capsella burswpastoris Echinochloacrus-galli Senecio vulgaris Galium aparine Stellaria media TABLEI-Continued COMPOUND 1 RATING NUMBERS ALLOCATED IN PRE-EMERGENCE TESTSDose w/v 0,008 0,02 0,04 0,06 0,2

MEAN RATING 0 0 0,3 0 3,5 NUMBER 0 0 l 2 4 0 0 0 2 4 WHEAT 0 0 0 3 0 0 40 I MEAN RATING 0 0 0,3 2 3,8 NUMBER 3,8 8.2 7,7 8,6 7.8 3,8 8,5 8,4 8,88,2 WEEDS 6,8 7,2 6,4 7,0 (mean of I2 weed 5,7 8,4 8,6

species) 4,2 8,1 8,5 6,7

MEAN RATING 4,8 7,6 7,7 8,7 7,9 NUMBER TABLE 2 COMPOUND DIURON RATINGNUMBERS ALLOCATED IN PREEME RGENCE TESTS As will be observed from'theTables, at the 0.06 and 0.2 concentrations, the degree of damage causedby diuron in wheat and carrots is the same as or higher than that in theweeds. At the 0.04 concentration, in wheat, again the degree of damageis greater than that caused in the weeds and in carrots in 50 percentthat caused in weeds. In no case tested could diuron be said to exercisebiological selectivity in carrots or wheat.

In the case of treatment with the compound of formula I on the otherhand, at the 0.04 concentration 200 percent more damage is caused in theweeds than in either the wheat or the carrots. At the 0.06concentration, complete selectivity is to be observed with regardcarrots with appreciable damage to the weeds, and more than four timesmore damage in the wheat than the weeds is observed. Even at the highestconcentration of 0.2, it can be seen that the degree of damage to thewheat and carrots is 50 percent less than that in the weeds. At thelower concentrations of 0.008 and 0.02,

complete selectivity with appreciable damage to the weeds is observed.

The conclusion to be drawn is that the compound of formulal at allconcentrations tested, maintains a damage differential between, on theone hand the carrots and the wheat, and on the other hand the weeds, andso a definite biological selectivity for the weeds. Diuron on the handshows no such damage differential and indeed, generally, more damage isobserved in the wheat and carrots than in the weeds.

EXAMPLE 2:

Post-emergent treatment A procedure similar to that of the pre-emergencetest described above is followed, excepting that the fifty ml ofherbicide solution is applied when the seed plants are at a 2-4 leafstage. In order that uniform treatment of various seed plants may beeffected at a time when each of the plant species has reached the 2-4leaf stage, the various seed species are sown in time staggeredrelationship.

As with the pre-emergence test, the prepared seed dishes treated withherbicide are kept for 28 days under the greenhouse conditionsdescribed. The determination of the herbicidal effect of the particularherbicide again involves a visual evaluation of the degree and qualityof damage to the various seed plants, and an allocation of a ratingnumber in the manner described.

The results obtained with compound I and Diuron are set out in thefollowing Tables 3 and 4. The weeds in the tests are the same as listedin the above preemergent test.

TABLE 3 COMPOUND I RATING NUMBERS ALLOCATED IN POST-EMERGENCE TESTS Dosew/v 0,008 0,02 0,04 0,06 0,2

0 0 0 0 I 0 3 0 0. 0 0 5 CARROT 0 0 2 0 0 2 0 .0 0 I MEAN RATING 0 1,50,1 0 2,0 NUMBER I 3 0 0 0 0 0 0 5 0 0 3 WHEAT 0 l 2 0 3 5 2 0 2 0 MEANRATING 0,5 I,5 0,8 0 3,0 NUMBER 8,0 8,5 8,8 8,9 5,3 8,3 7,6 8,7 8,9WEEDS 5,4 8,2 8,9 (mean of 12 weed 4,4 8,9 8,9

species) 4,7 7,0 7,5 8,1

MEAN RATING 5,2 8,2 8,1 8,8 8,9

NUMBER TABLE 4 COMPOU ND-Diuron RATING NUMBERS ALLOCATED INPOST-EMERGENCE TESTS The following Examples 3 to 6 are illustrative ofthe method of the present invention. These Examples concern field testsin the open, and confirm the indications obtained in a series ofgreenhouse tests, including those described above.

EXAMPLE 3:

Combating of weeds in cereals, small plot test in the open Plots of asize of square meters are separated off in a cereal field sown withwheat. When the germinated cereal has reached the 2 to 5 leaf stage, thesoil plots are sprayed with aqueous suspensions of diuron and thecompound offormula I respectively in a quantity corresponding to 1000litres of liquor and 2.5 kg of active agent per hectare. After 3 weeksthe weeds belonging to the group of monoand dicotyledons, i.e.Alopecuras spp. (A. myosuroides, A. pratensis), Amaranthus retro- Iflexus, Agrostis spica-venti, Atriplex patula, Capsella bursa-pastoris,Chenopodium album, Echinochloa crusgalli, Galeopsis tetrahit, Lamiumpurpureum, Poa annua, Polygonum convolvulus, Polygonum persicaria,Papaver rhoeas, Portulaca oleracea, Raphanus raphaniszrum, Stellariamedia and Thlaspi arvense, are destroyed. No damage can be ascertainedin the case of.

the cereal treated with the compound of formula I, but i the soiltreated with Diuron shows total damage to the cereal plants.

EXAMPLE 4:

Selective combating of weeds in winter by post-emergence process, smallplot test in the open air Plots of the size of 5 square metres, havingmainly a weed growth of Alapecurus myosuroides, Agrostis spicaventi andAvena fatus in addition to dicotyledons, are sprayed at a period whenthe winter wheat has 3-5 1 leaves with an aqueous suspension of thecompound of formula I in an amount corresponding to 3.5 kg per hectare.Evaluation after 28 days shows a complete herbicidal effect withinsignificant damage to the winter wheat.

In plots of land of the same size, treatment for purposes of comparisonwith Diuron in the same amount results in total damage to the winterwheat.

The compound of formula I is used with similar success for combatingweeds in summer wheat, winter and summer barley, and winter and summerrye. Winter wheat is likewise undamaged when the amount of compound l isincreased to 6 kilogram per hectare.

EXAMPLE 5:

Selective combating of weeds in carrots by pre-emergence process, smallplot test in the open Carrot seeds are sown in freshly dug fallow plotsof land of a size of 5 square meters, an earth covering is applied andon the same day spraying with an aqueous suspension of diuron and thecompound of formula respectively is effected, the amount correspondingto 4.5 kg of each active agent per hectare. A plot is kept untreated asa blank. Evaluation of the test after three weeks gives the resultsdescribed in the following Ta ble.

TABLE Active Agent l-lerbicidal Effect Damage to Carrots Diuron someplants of Planmgo complete major Compound of completely free of weedsinsigificant Formula 1 Blank germinated weeds:

Amaramhus retroflexus, Echinochloa crus-galli, Galinsoga parvifiora,Planlago major, Paa amzuu, Sinqpis arvelzsis,

Stellaria media, Polygonum persicaria, Polygonum mmolvulus, Ruphanusraplmnislru, Capsella bursapastoris and Galeopsis lzrralxil.

This test shows the excellent biological selective herbicidal effect ofthe compound of formula I as compared with the active agent used forpurposes of comparison; no damage to the culture resulted when 6kg/hectare of the compound of formula I were applied.

EXAMPLE 6 Selective combating of weeds in carrots by post emergence,small plot test in the open Plots of the size of 5 square metres havingmainly a weed growth of Amaranthus retroflexus, Echinachloa crus-galli,Galinsoga parviflora, Plantaga major and Sinapis arvensis and on whichcarrots had germinated after seeds of carrots had been sown, are treatedat a time when the carrots have reached the 4 leaf stage with aqueoussuspensions of diuron and the compound of formula I respectively in anamount corresponding to 4.5 kg per hectare. One plot is kept untreatedas a blank. Evaluation after 28 days gives the results shown below:

Active Agent Herbicidal Effect Damage to Carrots Diuron some plants ofPlanlago complete major Compound of completely free of weedsinsignificant formula I Blank strong weed growth l. A method ofselectively combatting weeds in a wheat locus to be protected from weedscomprising applying to the wheat locus the compound N-(3-chloro-4-methoxyphenyl)-N',N-dimethylurea in an amount of from 2 to kilograms perhectare of said wheat locus.

2. The method of claim 1 in which the amount of said compound applied tothe wheat locus is from 2 to 6 kilograms per hectare. v

3. The method of claim 1 in which the compound is applied after sowingbut prior to emergence of the wheat.

4. The method of claim 1 in which the compound is applied post-emergentwith respect to the wheat.

5. The method of claim 1 in which the wheat locus is a winter wheatlocus.

6. The method of claim 3 in which the amount of said compound applied tothe wheat locus is from 2 to 6 kilograms per hectare.

7. The method of claim 4 in which the amount of said compound applied tothe wheat locus is from 2 to 6 kilograms per hectare.

8. A method of selectively combatting weeds in a carrot locus to beprotected from weeds comprising applying to the carrot locus thecompound N-(3-chloro-4- methoxyphenyl)-N',N-dimethylurea in an amount offrom 2 to 10 kilograms per hectare of said carrot locus.

9. The method of claim 8 in which the amount of said compound applied tothe carrot locus is from 2 to 6 kilograms per hectare.

10. The method of claim 8 in which the compound is applied after sowingbut prior to emergence of the carrots.

11. The method of claim 8 in which the compound is applied post-emergentwith respect to the carrots.

1. A METHOD OF SELECTIVELY COMBATTING WEEDS IN A WHEAT LOCUS TO BE PROTECTED FROM WEEDS COMPRISING APPLYING TO THE WHEAT LOCUS THE COMPOUND N-(3-CHLORO-4-METHOXYPHENYL)N'',N''-DIMETHYLUREA IN AN AMOUNT OF FROM 2 TO 10 KILOGRAMS PER HECTARE OF SAID WHEAT LOCUS.
 2. The method of claim 1 in which the amount of said compound applied to the wheat locus is from 2 to 6 kilograms per hectare.
 3. The method of claim 1 in which the compound is applied after sowing but prior to emergence of the wheat.
 4. The method of claim 1 in which the compound is applied post-emergent with respect to the wheat.
 5. The method of claim 1 in which the wheat locus is a winter wheat locus.
 6. The method of claim 3 in which the amount of said compound applied to the wheat locus is from 2 to 6 kilograms per hectare.
 7. The method of claim 4 in which the amount of said cOmpound applied to the wheat locus is from 2 to 6 kilograms per hectare.
 8. A METHOD OF SELECTIVELY COMBATTING WEEDS IN A CARROT LOCUS TO BE PROTECTED FROM WEEDS COMPRISING APPLYING TO THE CARROT LOCUS THE COMPOUND N-(3-CHLORO-4-METHOXYPHENYL)N'',N''-DIMETHYLUREA IN AN AMOUNT OF FROM 2 TO 10 KILOGRAMS PER HECTARE OF SAID CARROT LOCUS.
 9. The method of claim 8 in which the amount of said compound applied to the carrot locus is from 2 to 6 kilograms per hectare.
 10. The method of claim 8 in which the compound is applied after sowing but prior to emergence of the carrots.
 11. The method of claim 8 in which the compound is applied post-emergent with respect to the carrots. 